Michael Cassel, Steffen Müller, Anja Carlsohn, Heiner Baur, N. Jerusel, Frank Mayer

• Background: Clinical examinations of tendon disorders routinely include ultrasound examinations, despite the fact that availability of data concerning validity criteria of these measurements are limited. The present study therefore aims to evaluate the reliability of measurements of Achilles- and Patella tendon diameter and in the detection of structural adaptations. Materials and Methods: In 14 healthy, recreationally active subjects both asymptomatic Achilles (AT) and patella tendons (PT) were measured twice by two examiners in a test-retest design. Besides the detection of anteroposterior (a.p.-) and mediolateral (m.l.-) diameters, areas of hypoechogenicity and neovascularisation were registered. Data were analysed descriptively with calculation of test-retest variability (TRV), intraclass-correlation coefficient (ICC) and Bland and Altman's plots with bias and 95% limits of agreement (LOA). Results: Intra- and interrater differences of AT- and PT-a.p.-diameter varied from 0.2 - 1.2 mm, those of AT- and PT-m.l-diameter fromBackground: Clinical examinations of tendon disorders routinely include ultrasound examinations, despite the fact that availability of data concerning validity criteria of these measurements are limited. The present study therefore aims to evaluate the reliability of measurements of Achilles- and Patella tendon diameter and in the detection of structural adaptations. Materials and Methods: In 14 healthy, recreationally active subjects both asymptomatic Achilles (AT) and patella tendons (PT) were measured twice by two examiners in a test-retest design. Besides the detection of anteroposterior (a.p.-) and mediolateral (m.l.-) diameters, areas of hypoechogenicity and neovascularisation were registered. Data were analysed descriptively with calculation of test-retest variability (TRV), intraclass-correlation coefficient (ICC) and Bland and Altman's plots with bias and 95% limits of agreement (LOA). Results: Intra- and interrater differences of AT- and PT-a.p.-diameter varied from 0.2 - 1.2 mm, those of AT- and PT-m.l-diameter from 0.7-5.1 mm. Areas of hypoechogenicity were visible in 24% of the tendons, while 15% showed neovascularisations. Intrarater AT-a.p.-diameters showed sparse deviations (TRV 4.5-7.4%; ICC 0.60-0.84; bias -0.05-0.07 mm; LOA-0.6-0.5 to -1.1 - 1.0 mm), while interrater AT- and PT-m.l.-diameters were highly variable (TRV 13.7-19.7%; ICC 0.11-0.20; bias -1.4-4.3 mm; LOA-5.5-2.7 to -10.5 - 1.9 mm). Conclusion: Our results suggest that the measurement of AT- and PT-a.p.-diameters is a reliable parameter. In contrast, reproducibility of AT- and PT-m.l.-diameters is questionable. The study corroborates the presence of hypoechogenicity and neovascularisation in asymptomatic tendons.…